An estimated 30-40% of school-aged children with an autism spectrum disorder (ASD) remain minimally verbal even after receiving years of interventions. These children require an intervention approach that simultaneously (a) consolidates early success in treatment and (b) intensifies treatment given signs of early non-response in order to place all children on a positive, long-term course. The overarching aim of this Network study is to construct an adaptive intervention that utilizes two efficacious interventions (JASP-EMT and CORE-DTT) that rely on distinct intervention procedures and that show promise for optimizing the number of unique socially communicative and spontaneously spoken words in minimally verbal children with ASD. JASP-EMT (Joint Attention, Symbolic Play and Enhanced Milieu Teaching) focuses on creating a context for joint engagement within naturally occurring, child-led play activities. CORE-DTT (discrete trial training for core features of ASD) emphasizes didactic, adult-led instruction. The study utilizes a novel sequential multiple assignment randomized trial to evaluate and construct an optimal adaptive intervention. Children will be initially randomized to six weeks of JASP-EMT or CORE-DTT (first-phase treatment). After six weeks, children will be assessed for early non/response. Early responders will be randomized to staying the course on first-phase treatment with therapist intervention or to therapist plus parent training. Early non-responders to either first- phase treatment will receive both JASP-EMT and CORE-DTT in an attempt to maximize language outcomes. Children will receive intervention daily at school for 4 months total. Outcome assessments will occur at 4 and 8 months. With support from a Data Coordinating Center involving SIStat at UCLA and University of Michigan, the study will enroll 192 children with ASD across four sites, Los Angeles, Nashville, New York and Rochester. The specific aims of the study are a) to determine which intervention (JASP-EMT vs. CORE-DTT) produces greater increases in socially communicative spontaneous utterances (SCU; primary outcome) and symbol- infused joint engagement, number of unique words, and object play level (secondary outcomes), b) to determine whether adding a parent training component provides additional benefit among participants who demonstrate a positive early response to either JASP-EMT or CORE-DTT, c) to compare and contrast four pre-specified adaptive interventions in terms of primary and secondary outcomes, and d) to determine whether baseline repetitive behavior, baseline object interest and parent expectancies for the specific intervention moderate intervention outcomes. This study has the potential to dramatically improve communication outcomes for children with ASD who are minimally verbal, and addresses a high priority need of the Interagency Autism Coordinating Council (2011). A Network of experienced researchers with complementary expertise is necessary to address this unmet priority.